Since the human genome is, essentially, shared by all, I suggest the differences
in race result from differences in gene expression. I suggest testosterone is
the molecule that causes major differences in gene expression, that result in
the differences described as "race." Humans and chimpanzees exhibit major
differences in testosterone; human "races" exhibit major differences in
testosterone. Changes in testosterone, along with only slight differences in
genes, will produce the appearance of different species of hominids over time.
James Howard